Growth Promotion Of Seedlings Research Articles

Glomus–Azotobacter association affects phenology of mango seedlings under reduced soil nutrient supply

The aim of this research was designed to determine the effectiveness of indigenous arbuscular mycorrhizal (AM) fungal species Glomus fasciculatum (Thaxter sensu Gerdemann), Glomus magnicaulis (Hall) and Azotobacter strains on growth promotion of mango seedlings under limited nitrogen (N) and phosphorous (P) soil fertilization for sustainable nursery management in rainfed ecosystem. Three districts in the state of Himachal Pradesh namely, ‘Kangra’, ‘Hamirpur’ and ‘Bilaspur’ being located in the Shiwalik hill range of north-western Himalayas of India were selected purposely to measure the intensity of occurrence and distribution of indigenous AM fungal species and A. chroococcum strains in local ‘Dashehari’ mango orchards. AM fungi viz., G. fasciculatum (Thaxter sensu Gerdemann), G. magnicaulis (Hall), G. mosseae (Nicol. and Gerd.) and Gigaspora heterogamma (Nicol. and Gerd.), and two strains of A. chroococcum viz., AZ1 and AZ2 were predominant in the rhizosphere soil of the orchards. The data inferred that AM fungal spore load, root colonization and A. chroococcum bacterial count in different locations ranged from 2150–2975 sporeskg−1 of the moist soil, 8.5–11.8% and 3.1×106–4.7×106 colony forming units (cfu), respectively. Soil type of the orchards varied between sandy loam and clay loam. To assess the comparative effectiveness of AM species and Azotobacter strains, the inocula were screened alone and in dual combination at different levels of N and P inorganic fertilizers. The inocula of potent isolates/strains i.e., Glomus fasciculatum, G. magnicaulis, AZ1 and AZ2 were multiplied and inoculated under varied N and P fertilization in the ratio of 12:4gkg−1 i.e. 2/3 N+P, 3/4 N+P and full N+P. Vegetative development affected by the mycorrhizal and bacterial inoculation was more pronounced when seedlings were inoculated with G. fasciculatum followed by G. magnicaulis with AZ1 and/or AZ2 alone, and in dual combination at 2/3 dose of N+P. The inoculation of either of AM fungal species and/or bacterial strains led to a significant increase in plant height, stem diameter, leaf area and total root length in comparison to non-inoculated control, and was also demonstrated with G. fasciculatum and AZ1 stimulated maximum growth of the seedlings in reduced N and P inorganic fertilizer sources. Considering the overall results, G. fasciculatum and AZ1 had a greater effect on vegetative growth promotion in reduced soil nutrient supply on mango seedlings.

Effect of zoysiagrass rhizosphere fungal isolates on disease suppression and growth promotion of rice seedlings

Some rhizosphere fungal isolates belonging to Phoma, Penicillium, Trichoderma and Fusarium were evaluated to control Fusarium and Rhizopus blights and bakanae diseases of rice seedlings. Among the isolates, Phoma spp. GS8-2, GS6-4 and GS10-2 showed 74–89% reduction of severity of Fusarium blight in rice seedlings. In case of Rhizopus blight, Phoma spp. GS8-2, GS6-4 and GS12-2 and Trichoderma harzianum GT3-2 reduced disease severity to 81–93%. Phoma sp. GS12-2 was the most effective isolate in controlling bakanae disease (90% reduction in disease severity). The effect of the tested isolates on the growth of rice seedlings varied significantly in terms of fresh and dry weight in rice trays. However, Phoma sp. GS12-2 effectively increased fresh and dry weight of shoots to 40 and 30%, respectively, compared with untreated control plants. In contrast, Phoma sp. GS6-4, T. harzianum GT3-2 and Penicillium sp. GP17-1 showed inhibitory effect to shoot growth of rice seedlings.

Testing of Bacterial Endophytes from Non-Host Sources as Potential Antagonistic Agents against Tomato Wilt Pathogen <i>Ralstonia solanacearum</i>

The study was taken up with the objective of testing whether the endophytic organisms isolated from crops that are normally non-hosts to the bacterial wilt pathogen Ralstonia solanacearum possessed pathogen-antagonistic activity and to evaluate the selected isolates for the alleviation of wilt disease in the target tomato crop through horizontal movement of promising organisms. Sixteen endophytic bacteria (EB) isolated from the micropropagated cultures of grape, watermelon and papaya were tested for potential antagonistic effects against R. solanacearum tomato isolate “NH-01” through agar-well diffusion assay. Enterobacter cloacae from papaya (EB-11) displayed the maximum antagonistic effect followed by Bacillus subtilis (EB-06) and B. flexus (EB-07) from watermelon and B. pumilus (EB-02) from grape. Testing the above organisms for crop protection through seed fortification of susceptible tomato cv. Arka Vikas at sowing in R. solanacearum inoculated (Ral+) organic cocopeat showed EB-02 and EB-11 promising (33% and 32% survival, respectively, four weeks after sowing against 15% in Ral+ control). A second trial showed 37%, 28%, 21% and 55% seedling survival 6 weeks after sowing for EB-02, EB-06, EB-07 and EB-11 respectively, compared to 2.5% in non-treated control. Assessing the four endophytes for crop protection in Ral+ sick-soil through seedling fortification at transplanting indicated less disease incidence in treated sets (40%, 40%, 20% and 20% survival, respectively, six weeks after transplanting) over non-fortified control (5%). Endophytic fortification of seedlings through hypocotyl inoculation showed some systemic resistance induction upon seedling transplanting to sick soil but not with petiole fortification. Seedling growth was enhanced by the isolates EB-06 and EB-07. The study thus identifies four endophytic organisms from crops unrelated to tomato possessing potential antagonistic activity against the wilt pathogen and prospects for exploitation as biocontrol agents coupled with seedling growth promotion effects.

근권 Trichoderma harzianum MPA167 처리에 의한 생육촉진과 고추 역병균에 대한 고추의 유도저항성

Trichoderma harzianum 은 식물의 뿌리주변에 살아가는 근권미생물 중의 하나로 여러 가지 식물에 생육을 촉진하며 식물의 병저항성을 증강시킨다. 본 연구로부터 선발된 T. harzianum MPA167은 보리의 근권 등으로부터 분리된 183종의 트라이코데르마 균주로부터 선발되었으며 고추역병균인 Phytophthora capsici에 대한 억제효과가 우수함을 구명하였다. T. harzianum MPA167균주는 23s rDNA ITS sequences 분석 결과 T. harzianum 으로 동정하였다. 본 균주(<TEX>$1{\times}10^6$</TEX> spores/ml)의 처리는 고추역병의 방제에 가장 효과적이었으며 이 균주가 생산하는 휘발성 생육촉진물질은 담배 및 애기장대 식물의 생육을 크게 증가 시켰다. 또한 본 균주의 처리로 고추의 생육촉진과 유도저항성이 발현되었다. 이와 같은 결과로 보아 본 선발 균주인 T. harzianum MPA167는 작물의 생육촉진과 생물방제를 위한 친환경 농자재로의 활용이 가능 할것으로 생각된다. Trichoderma harzianum is one of rhizosphere fungus usually lives near the plant root regions in the soil. T. harzianum plays an important role in plant growth promotion and increases disease resistance against various plant pathogens on crops. In this study, the strain T. harzianum MPA167 was isolated from the barley rhizosphere soil in Suwon, Korea. Among 183 isolates, the strain T. harzianum MPA167 was selected as promising strain in which based on hyperparasitical activity against Phytophthora capsici and estimated disease control activity against P. capsici in the greenhouse conditions. The strain T. harzianum MPA167 was identified using 23s rDNA internal transcribed spacer(ITS) region sequences. MPA167 treatment (<TEX>$1{\times}10^6$</TEX> spores/ml) showed greater disease suppression against Phytophthora blight of red-pepper caused by P. capsici in greenhouse compared with the water-treated control. Volatiles derived from T. harzianum MPA167 elicit growth promotion of tobacco and Arabidopsis seedlings in I-plate assay. In addition, T. harzianum MPA167 strain was also found to be effective for the growth promotion and induction of systemic resistance on red-papper plant. These results suggest that MPA167 might be used as one of the potential biocontrol agents.

Growth Promotion of Tobacco Plant by 3-hydroxy-2-Butanone from Bacillus vallismortis EXTN-1

It has been well documented that Bacillus vallismortis strain EXTN-1, a beneficial rhizosphere bacterium, could enhance plant growth and induce systemic resistance to diverse pathogens in plants. However, the molecular mechanisms for how the EXTN-1 promote plant growth and induce resistances to diverse pathogens. Here, we show that 3-Hydroxy-2-butanone, a volatile organic compound (VOCs) emitted from the EXTN1, is a key factor for the bacteria-mediated beneficial effects on plant growth and defense systems. We found that the presence of volatile signals of EXTN-1 resulted in growth promotion of tobacco seedlings. The identification and analysis of EXTN-1-secreted volatile signals by solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) indicated that a 3-hydroxy-2-butanone could provide not only the plant growth promotion, but also higher resistance against Pectobacterium carotovorum SCC1. These results suggest that a volatile compound released from EXTN-1 enhances the plant growth promotion and immunity of plants.

Growth promotion of rice seedlings by fungal and bacterial bioagents effective against bacterial leaf blight of rice

In the present investigation, fungal and bacterial bioagents which were effective against pathogen of bacterial leaf blight disease of rice (Xanthomonas oryzae pv. oryzae) was tested for their effect on germination of rice seeds and growth of nursery seedlings under laboratory and glasshouse conditions. Two isolates of fluorescent pseudomonas isolated from rice phylloplane (Pf 83 and FLP 88), Trichoderma species were isolated from soil of rice field (isolate 40) and Trichoderma harzianum isolated from rice phylloplane. Two commercial formulations (PBA-1 and PBA-2) were tested in the present investigation and compared with chemical treatment (0.76 g Emison + 0.18 g Streptocycline / kg seeds) and untreated check. Under laboratory conditions, chemical treatment was found most effective in increasing seed germination (43.90%) followed by Pf 83 and PBA-1 (34.15 %). Bioagent formulations were significantly effective in increase in root and shoot length as compared to check and chemical treatment. Under glasshouse conditions, maximum increase (29.42%) in seedlings emergence was exhibited by chemical treatment. Maximum increase in root length (100.15%) and shoot length (50.06%) was recorded with FLP 88 and T. harzianum, respectively. Bioagent formulations also increased fresh and dry root weight over check and chemical treatment. All bioagents formulations were effective over chemical treatment and check in increasing fresh shoot weight. Results of the present study revealed that in the absence of pathogen of bacterial leaf blight of rice, fungal and bacterial bioagents significantly enhanced germination of rice seeds and growth of nursery seedlings.

Influence of Bacillus spp. strains on seedling growth and physiological parameters of sorghum under moisture stress conditions

Microorganisms isolated from stressed ecosystem may prove as ideal candidates for development of bio-inoculants for stressed agricultural production systems. In the present study, moisture stress tolerant rhizobacteria were isolated from the rhizosphere of sorghum, pigeonpea, and cowpea grown under semiarid conditions in India. Four isolates KB122, KB129, KB133, and KB142 from sorghum rhizosphere exhibited plant growth promoting traits and tolerance to salinity, high temperature, and moisture stress. These isolates were identified as Bacillus spp. by 16S rDNA sequence analysis. The strains were evaluated for growth promotion of sorghum seedlings under two different moisture stress conditions (set-I, continuous 50% soil water holding capacity (WHC) throughout the experiment and set-II, 75% soil WHC for 27 days followed by no irrigation for 5 days) under greenhouse conditions. Plate count and scanning electron microscope studies indicated successful root surface colonization by inoculated bacteria. Plants inoculated with Bacillus spp. strains showed better growth in terms of shoot length and root biomass with dark greenish leaves due to high chlorophyll content while un-inoculated plants showed rolling of the leaves, stunted appearance, and wilting under both stress conditions. Inoculation also improved leaf relative water content and soil moisture content. However, variation in proline and sugar content in the different treatments under two stress conditions indicated differential effect of microbial treatments on plant physiological parameters under stress conditions.

The endophyte Enterobacter sp. FD17: a maize growth enhancer selected based on rigorous testing of plant beneficial traits and colonization characteristics

With the aim to select powerful microbial strains to be used for the enhancement of maize yield and resistance to abiotic and biotic stresses, we tested five endophytic bacterial strains previously isolated from maize roots. A range of different laboratory assays in regard to potential plant growth promotion was performed and strains were further evaluated for improving growth of five maize cultivars under axenic and natural soil conditions. Endophytic colonization was an additional component in our selection process as it is of high importance for an inoculant strain to efficiently colonize the plant environment. All strains had the potential to improve maize seedling growth under axenic conditions. Enterobacter sp. strain FD17 showed both the highest growth-promoting activity under axenic conditions as well as colonization capacity. FD17 was therefore selected for further plant tests in a net house, in which two different maize cultivars were grown in large pots until ripening and subjected to outdoor climatic conditions. Results showed that inoculation significantly increased plant biomass, number of leaves plant−1, leaf area, and grain yield up to 39 %, 14 %, 20 %, and 42 %, respectively, as compared to the un-inoculated control. Similarly, inoculation also improved the photochemical efficiency of photosystem II (PSII) of maize plant and reduced the time needed for flowering. We also confirmed that strain FD17 is able to colonize the rhizosphere, roots and stems. Based on rigorous testing, Enterobacter sp. strain FD17 showed the highest potential to promote growth and health of maize grown under natural conditions. This study suggested that in vitro plant growth-promoting traits and potential of maize seedling growth promotion by bacterial endophytes could be used for the selection of potential inoculant strains subjected for further testing as bio-inoculant under field conditions.

N2-Fixation and Seedling Growth Promotion of Lodgepole Pine by Endophytic Paenibacillus polymyxa

We inoculated lodgepole pine (Pinus contorta var. latifolia (Dougl.) Engelm.) with Paenibacillus polymyxa P2b-2R, a diazotrophic bacterium previously isolated from internal stem tissue of a naturally regenerating pine seedling to evaluate biological nitrogen fixation and seedling growth promotion by this microorganism. Seedlings generated from pine seed inoculated with strain P2b-2R were grown for up to 13 months in a N-limited soil mix containing 0.7 mM available N labeled as Ca((15)NO3)2 to facilitate detection of N2-fixation. Strain P2b-2R developed a persistent endophytic population comprising 10(2)-10(6) cfu g(-1) plant tissue inside pine roots, stems, and needles during the experiment. At the end of the growth period, P2b-2R had reduced seedling mortality by 14 % and (15)N foliar N abundance 79 % and doubled foliar N concentration and seedling biomass compared to controls. Our results suggest that N2-fixation by P. polymyxa enhanced growth of pine seedlings and support the hypothesis that plant-associated diazotrophs capable of endophytic colonization can satisfy a significant proportion of the N required by tree seedlings growing under N-limited conditions.

Growth Promotion of Yunnan Pine Early Seedlings in Response to Foliar Application of IAA and IBA

A field experiment was conducted using a 3 × 3 orthogonal regression design to explore the growth promotion of one-year-old Yunnan pine seedlings (Pinus yunnanensis Franch.) in response to foliar application of IAA (indole-3-acetic acid) at rates of 0, 200 and 400 mg·L−1 and IBA (indole-3-butyric acid) at rates of 0, 200 and 400 mg·L−1 in order to promote the growth during the seedlings’ early stage. The experiment was conducted at the Lufeng Village Forest Farm of Yiliang County in Kunming, Yunnan, China. The results showed that IAA and IBA were effective in growth promotion of Yunnan pine seedlings. The response of both growth increment and biomass accumulation to the concentration of IAA and IBA can be modeled using a bivariate surface response, and each growth index had a peak value. Growth indexes increased with the increase of the dosage of photohormones before reaching a peak value, and then decreased. The different growth indexes had various responses to the concentrations and ratio of IAA and IBA. The foliar application of IAA in combination with IBA showed the largest improvement on the biomass of the needles, followed by stems and roots. The higher ratio of IAA promoted stem diameter growth, root system development and biomass accumulation in the needles, while a higher ratio of IBA contributed to height growth and biomass accumulation in the stem. Based on the auxin effect equations on the different growth indexes and surface response, the optimum concentrations and the (IAA:IBA) ratios can be obtained. The optimum concentrations of IAA and IBA were 167 and 186, 310 and 217, 193 and 159, 191 and 221, and 206 and 186 mg·L−1, with corresponding ratios of 1:1.11, 1:0.70, 1:0.82, 1:1.15 and 1:0.90, respectively, at the maximum seedling height and collar diameter growth as well as biomass accumulation at the root, stem and needle. The above growth indexes were 22.00%, 79.80%, 48.65%, 82.20% and 107.00% higher than the control treatment.

Influence of inoculation with a Trichoderma bio-inoculant on ectomycorrhizal colonisation of Pinus radiata seedlings

Trichoderma species, through mechanisms such as mycoparasitism, antibiosis, induced resistance and competition, are able to suppress the growth and activity of soil microbes and therefore have the potential to influence ectomycorrhizal (ECM) fungal colonisation. ECM colonisation potential of Pinus radiata seedlings inoculated with the commercially available Trichoderma species bio-inoculant, ArborGuard™, was investigated in a commercial containerised nursery setting and in a separate glasshouse experiment. Application of ArborGuard™ to P. radiata seedlings in both the containerised nursery and glasshouse experiment had no detrimental effect on the ability of the naturally occurring ECM fungi to colonise the seedlings. Thelephora terrestris was the only ECM species colonising the P. radiata root tips in the containerised system while Tomentella ellisii was the dominant species found colonising the P. radiata root tips in the glasshouse experiment. No seedling growth promotion was observed with the addition of ArborGuard™. The results show that the Trichoderma bio-inoculant ArborGuard™ does not affect ECM colonisation of P. radiata seedlings by Th. terrestris and T. ellisii in a containerised nursery system.

Biocontrol of seed pathogens and growth promotion of common bean seedlings by Trichoderma harzianum

The objective of this work was to evaluate isolates of Trichoderma harzianum regarding biocontrol of common bean seed-borne pathogens, plant growth promotion, and rhizosphere competence. Five isolates of T. harzianum were evaluated and compared with commercial isolate (Ecotrich), Carboxin+Thiram, and an absolute control. Bean seeds of the cultivar Jalo Precoce, contaminated with Aspergillus, Cladosporium, and Sclerotinia sclerotiorum, were microbiolized with antagonists, and seed health tests were carried out. Isolates were evaluated on autoclaved substrate and in field conditions. Ten days after sowing (DAS), plant length was measured. To test rhizosphere competence, isolates were applied in boxes containing autoclaved washed sand, and root colonization was evaluated at 10 DAS, using five plants per box. The most effective isolates in the seed health tests were: CEN287 and CEN289 to control Aspergillus; the commercial isolate to control Cladosporium; and CEN287 and CEN316 to control S. sclerotiorum. Isolates CEN289 and CEN290 promoted bean growth in greenhouse and field. Seed treatment with T. harzianum reduces the incidence of Aspergillus, Cladosporium, and S. sclerotiorum in 'Jalo Precoce' common bean seeds.

Indução de resistência sistêmica por rizobactérias em cultivos hidropônicos

Rizobactérias do grupo fluorescente de Pseudomonas spp. foram selecionadas quanto a sua capacidade na promoção de crescimento em plântulas de alface (Lactuca sativa L.) e atividade antagônica contra Pythium aphanidermatum a partir de teste in vitro. Em seguida, em sistema hidropônico, foi avaliada a aplicação prévia dos isolados visando reduzir os danos provocados por P. aphanidermatum em pepino (Cucumis sativus) por resistência sistêmica induzida (RSI), pela adoção da técnica "raízes subdivididas". As variáveis massa da matéria seca (parte aérea e raízes) e comprimento radicular foram utilizadas na avaliação. A produção de compostos antagônicos e/ou promotores de crescimento pelos isolados de Pseudomonas spp. fluorescente foi verificada de modo a associar sua atividade com os resultados obtidos nos testes in vitro e em hidroponia. No experimento in vitro os isolados Ps 140B e Ps 140C proporcionaram maior crescimento das plantas (raiz e hipocótilo) de alface nos tratamentos com e sem patógeno. Alguns dos isolados avaliados no experimento hidropônico demonstraram uma possível expressão da RSI. Não houve correspondência entre os compostos produzidos e a promoção de crescimento vegetal ou controle da doença.

Occurrence of plant growth-promoting traits in clover-nodulating rhizobia strains isolated from different soils in Rio Grande do Sul state

In the last decades, the use of plant growth-promoting rhizobacteria has become an alternative to improve crop production. Rhizobium leguminosarum biovar trifolii is one of the most promising rhizobacteria and is even used with non-legume plants. This study investigated in vitro the occurrence of plant growth-promoting characteristics in several indigenous R. leguminosarum biovar trifolii isolated from soils in the State of Rio Grande do Sul, Brazil. Isolates were obtained at 11 locations and evaluated for indoleacetic acid and siderophore production and inorganic phosphate solubilization. Ten isolates were also molecularly characterized and tested for antagonism against a phytopathogenic fungus and for plant growth promotion of rice seedlings. Of a total of 252 isolates, 59 produced indoleacetic acid, 20 produced siderophores and 107 solubilized phosphate. Some degree of antagonism against Verticillium sp. was observed in all tested isolates, reducing mycelial growth in culture broth. Isolate AGR-3 stood out for increasing root length of rice seedlings, while isolate ELD-18, besides increasing root length in comparison to the uninoculated control, also increased the germination speed index, shoot length, and seedling dry weight. These results confirm the potential of some strains of R. leguminosarum biovar trifolii as plant growth-promoting rhizobacteria.

Growth promotion of wheat seedlings by Exiguobacterium acetylicum 1P (MTCC 8707) a cold tolerant bacterial strain from the Uttarakhand Himalayas

Exiguobacterium acetylicum strain 1P (MTCC 8707) is a gram-positive, rod-shaped, yellow pigmented bacterium isolated from soil on nutrient agar plates at 4°C. The identity of the bacterium was arrived on the basis of the biochemical characterization, BIOLOG sugar utilization pattern and sequencing of the 16S rRNA gene. It grew at temperatures ranging from 4 to 42°C, with temperature optima at 30°C. It expressed multiple plant growth promotion attributes such as phosphate solubilization, indole acetic acid (IAA), siderophore and hydrogen cyanide (HCN) production, differentially at suboptimal growth temperatures (15 and 4°C). At 15°C it solubilized phosphate (21.1 μg of P ml(-1) day(-1)), and produced IAA (14.9 μg ml(-1) day(-1)) in tryptophan amended media. Qualitative detection of siderophore production and HCN were possible at 15°C. At 4°C it retained all the plant growth promotion attributes. Seed bacterization with the isolate, positively influenced the growth and nutrient uptake parameters of wheat seedlings in glass house studies at suboptimal cold growing temperatures.

Produção de mudas de tomateiro em substrato orgânico inoculado e incubado com estreptomicetos

Este trabalho teve como objetivo avaliar a inoculação e incubação do substrato Plantmax® Hortaliças de produção de mudas, com diferentes isolados de estreptomicetos no crescimento de mudas de tomateiro. No primeiro ensaio, avaliou-se a inoculação de quatro isolados de actinomicetos e a testemunha não inoculada, sem incubação e com 20 dias de incubação, em esquema fatorial (5 x 2) e delineamento experimental de blocos casualizados, com 15 repetições. A inoculação e incubação do substrato com os estreptomicetos promoveram o aumento na altura das plantas, a produção de massa seca da parte aérea e raízes e o acúmulo de nutrientes na parte aérea das mudas de tomateiro. No segundo ensaio, avaliou-se a inoculação dos dois melhores estreptomicetos na promoção do crescimento das plantas de tomateiro produzidas em substrato orgânico incubado por cinco períodos diferentes (0, 15, 30, 45 e 60 dias), em esquema fatorial 2 x 5 e delineamento inteiramente casualizado, com oito repetições. Quarenta e três dias foi o melhor período para incubação, provavelmente, por ser o tempo necessário para que os estreptomicetos pudessem colonizar e atuar na decomposição do substrato orgânico, disponibilizando nutrientes para as raízes e permitindo o crescimento vegetal.

Early Growth Promotion and Charcoal Rot Suppression in Sorghum by Plant Growth Promoting Rhizobacteria

Thirty rhizobacterial isolutes from sorghum were evaluated for potential for seedling growth promotion and charcoal rot suppression in sorghum. Seven isolates repeatedly promoted early stage plant growth on the sorghum eultivar M35-I. Few isolates increased seed germination up to 43 percent and improved biotuass up to 66 percent on 30-day-old seedlings. Two isolates of fluorescent pseudomonads showed combined efficacy lor seedling growth promotion and disease suppression and reduced charcoal rot incidence considerably. In vitro properties of these isolates such as growth hormone, siderophore, HCN and ammonia prodnction, P-solubilization, antibiosis and production of volatile growth inhibitor have been discussed in relation to plant growth promotion and disease suppression.

The promotion of tomato and okra seedling growth by foliar applications of smoke–water and a smoke-isolated butenolide

The promotion of tomato and okra seedling growth by foliar applications of smoke–water and a smoke-isolated butenolide

Growth of Nursery-grown Bamboo Inoculated with Arbuscular Mycorrhizal Fungi and Plant Growth Promoting Rhizobacteria in two Tropical Soil Typeswith and without Fertilizer Application

A nursery experiment was conducted to assess the effect of bioinoculants (Glomus aggregatum, Bacillus polymixa, Azospirillum brasilense) on seedling growth promotion of bamboo (Dendrocalamus strictus (Roxb.) Nees.) in two soil types (alfisol, vertisol) with or without fertilizer application. Bamboo seedlings were grown in the presence or absence of bioinoculants either individually or in all combinations for 180 days in field soil under tropical nursery conditions. Shoot, rhizome and root length, dry masses, nutrient concentrations and arbuscular mycorrhizal (AM) colonized root lengths were determined at harvest. Under the experimental condition tested combined inoculation of AM fungi, PSB and A. brasilense resulted in maximum growth response both under fertilized and unfertilized conditions in both soil types. Fertilizer application enhanced the efficiencies of N, P and K uptake, whereas reduced their usage efficiencies. Though soil type did not affect microbial inoculation response, fertilizer application significantly affected plant response to microbial inoculation.

Rhizobacteria Isolated from Loblolly Pine Seedlings Mediate Growth-Promotion of Greenhouse-Grown Loblolly, Slash, and Longleaf Pine Seedlings

Abstract Loblolly (Pinus taeda L.), slash (Pinus elliottii Engelm.), and longleaf pine (Pinus palustris Mill.) seeds were inoculated in the greenhouse with rhizobacteria recovered from 4-month-old bareroot loblolly pine seedlings. Emergence and seedling densities were determined at 3- and 8-week intervals after sowing, respectively, with root and shoot biomass measured at 12 weeks. All bacterial strains significantly increased the speed of seedling emergence relative to untreated loblolly and slash pine seeds, while five strains significantly slowed longleaf germination. For loblolly and slash pine, there were no differences in percentage germination when comparing treated and untreated seed. However, all bacterial strains significantly reduced longleaf germination over nontreated seed. Treatment with rhizobacteria had significant positive and negative effects on seedling growth and biomass, depending on the tree species and bacteria isolate used. Five of the eight bacterial isolates tested increased shoot length of loblolly pine seedlings, whereas one strain increased above- and belowground biomass. Slash pine seedlings experienced growth increases with three bacterial strains. However, two bacterial strains, ALA-41G and ALA-54G, resulted in shorter slash pine shoots. Only strain ALA-3G increased shoot biomass of longleaf pine over nontreated longleaf seed. Increased seedling emergence and growth promotion by rhizobacteria collected from Pinus sp. is a potential useful tool for management of these forest species. The effect may be species-specific and the use of bacteria in forest nurseries for growth promotion will need to take this into account. FOR. SCI. 51(6):541–545.